Fluorescent reagents for live cell imaging and their introduction into cells

Most biological specimens, including Drosophila tissues, are relatively transparent, so details of internal and intracellular morphology are difficult to image in untreated living specimens using simple bright-field techniques. Although there are methods for improving contrast in bright-field imaging, fluorescence microscopy offers greater advantages and possibilities for increasing contrast and determining the specific localization of molecules in cells. Fluorescence microscopy has proven to be particularly well suited to the study of live material, now that an ever-increasing and bewildering array of different "vital" probes are available for tracking cellular components and activities, including some that have been applied to Drosophila. Here we outline the three methods most commonly used to introduce an appropriate label into Drosophila tissue without unduly perturbing the process.